Re: [kvm-unit-tests PATCH v2 7/8] arm64: microbench: Add time limit for each individual test

[Andrew Jones <drjones@redhat.com>]

On Thu, Jul 02, 2020 at 11:01:31AM +0800, Jingyi Wang wrote:
> Besides using separate running times parameter, we add time limit
> for loop_test to make sure each test should be done in a certain
> time(5 sec here).
> 
> Signed-off-by: Jingyi Wang <wangjingyi11@huawei.com>
> ---
>  arm/micro-bench.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/arm/micro-bench.c b/arm/micro-bench.c
> index 506d2f9..4c962b7 100644
> --- a/arm/micro-bench.c
> +++ b/arm/micro-bench.c
> @@ -23,6 +23,7 @@
>  #include <asm/gic-v3-its.h>
>  
>  #define NTIMES (1U << 16)
> +#define MAX_NS (5 * 1000 * 1000 * 1000UL)

How about naming this something like "NS_5_SECONDS"?

>  
>  static u32 cntfrq;
>  
> @@ -258,22 +259,26 @@ static void loop_test(struct exit_test *test)
>  	uint64_t start, end, total_ticks, ntimes = 0;
>  	struct ns_time total_ns, avg_ns;
>  
> +	total_ticks = 0;
>  	if (test->prep) {
>  		if(!test->prep()) {
>  			printf("%s test skipped\n", test->name);
>  			return;
>  		}
>  	}
> -	isb();
> -	start = read_sysreg(cntpct_el0);
> -	while (ntimes < test->times) {
> +
> +	while (ntimes < test->times && total_ns.ns < MAX_NS) {
> +		isb();
> +		start = read_sysreg(cntpct_el0);
>  		test->exec();
> +		isb();
> +		end = read_sysreg(cntpct_el0);
> +
>  		ntimes++;
> +		total_ticks += (end - start);
> +		ticks_to_ns_time(total_ticks, &total_ns);
>  	}
> -	isb();
> -	end = read_sysreg(cntpct_el0);
>  
> -	total_ticks = end - start;
>  	ticks_to_ns_time(total_ticks, &total_ns);
>  	avg_ns.ns = total_ns.ns / ntimes;
>  	avg_ns.ns_frac = total_ns.ns_frac / ntimes;
> -- 
> 2.19.1
> 
>

Thanks,
drew